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Winter Storm Could Push Spring Flood Risk Even Higher

More Snow Falls on Near Record Snowpack
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Chris Spears By Chris Spears
CBS4 Meteorologist
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DENVER (CBS4) – In a state like Colorado, where water is a crucial natural resource, snow is usually a welcomed sight, especially when it falls in the high country. But as a new winter storm moves in, forecasters are keeping a close eye on how new snowfall could change the risk for flooding later this spring.

As of March 24, snowpack in the South Platte River basin, which includes the entire Front Range and Denver metro area, was the third highest in over 30 years; only 1986 and 1996 were higher.

FLOOD FORECASTING

It can be difficult to create a flood forecast during any spring melt season because of the crucial role that changing temperatures play along with additional rain and snow. There are some new challenges complicating things this year, including a record snowpack and unforeseen impacts from last September’s heavy rain and devastating flash flood.

CONCERN IN THE FOOTHILLS

The 2013 flood forever changed the landscape of the northern Front Range foothills. Debris flows and landslides rerouted rivers, creeks and streams, changing how they will behave as water levels rise from snowmelt. In other areas, the swift moving waters eroded stream banks and created dams as large boulders and rubble piled up.

Soils remain saturated across much of the flood zone and there have been unusual phenomena reported over the past several months that are a direct result of the flood; these include springs flowing out of the ground that have never been seen, and fields that still have standing water, such as near 96th and Tower Road, not too far from Denver International Airport.

There’s also an increased chance for geologic events in the flood zone, including large mud slides. And some reservoirs remain at or near capacity and threaten to overflow, depending on how fast the snow melts and if more rain and snow fall.

OUTLOOK

The latest flood outlook from the National Weather Service places the highest potential for flooding along St. Vrain Creek, Boulder Creek, the Big Thompson River and the upper Cache La Poudre River. Flood risk is elevated in the north-central mountains, northern Front Range foothills and along the adjacent plains, including southwestern Weld County.

The immediate Denver area, south of Broomfield, has a normal flood risk this spring, along with the northeast plains.

Fingers are crossed that over the next several weeks, Mother Nature will help minimize this spring’s flood risk, with a gradual rise in temperature, which would allow the snow to melt at a slow and steady pace. A rapid warm up or an extended period of warm weather would be bad news, especially if combined with any significant spring storms.

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